EP 2 557 233 A1 discloses an implement with a hydraulic drive for underground construction work, which implement may be, in particular, a ramming device or drilling device.
In order to permit the implement to be adapted to the respective power requirements, a sensor for measuring the fluid pressure is arranged in a hydraulic circuit of the implement and is connected to an open-loop and closed-loop control unit. Both the displacement volume of the adjustable hydraulic motor and an internal combustion engine which is provided for rotating an adjustable hydraulic pump can be controlled by means of this open-loop and closed-loop control unit.
EP 2 557 233 A1 is concerned with the problem that during drilling or also vibration of ramming a maximum rotational speed or a predefined frequency range should not be departed from. At the start of such underground construction work the loading and therefore also the power requirement are still low so that only a small power level also has to be made available by the internal combustion engine. In order to cope with these requirements and, in particular, make available different power levels of the implement, a hydraulic transmission which is known per se is used, wherein the rotational speed of the internal combustion engine is also taken into account. Similar concepts are also described, for example, in DE 20 2007 014 676 A1, DE 27 00 803 A1, DE 2 236 134 and DE 38 06 194.
The present invention relates specifically to a vibrating ram arrangement according to the brochure “Müller-Vibratoren. Die perfekte Lösung zum Rammen and Ziehen [Müller Vibrators, the perfect solution for ramming and drawing]”, ThyssenKrupp GfT Bautechnik GmbH May 2011. The vibrator as a hydraulically driven machine is arranged above a vibration isolator here, for example on the hook of a crane, and is spatially separated from the hydraulic assembly. The hydraulic assembly with the hydraulic pump is connected to the vibrator via flexible hoses and is therefore isolated from the generation of the vibrations.
Owing to the very large mechanical loading on the vibrator, as a rule control electronics are dispensed with on the vibrator itself, wherein the operator control and adjustment of the vibrator is carried out via the hydraulic assembly. Even the arrangement of electronic sensors is problematic owing to the extreme mechanical loading and can lead to an increased risk of failure, for which reason the use of such sensors and other electronic devices such as servo drives is to be avoided as far as possible.